A wireless mesh network has received attention as a backhaul network of a low cost mobile communication infrastructure. In the wireless mesh network, base nodes are relayed and connected by a dedicated wireless link, which eliminates the necessity of installation of wireline backhaul and greatly reduces installation cost required for introduction of a mobile communication system. In the future, shrinkage of cell size is inevitable in the broadband communication, and it is necessary to install an extremely large number of base nodes. Accordingly, the installation cost of the base nodes increases to cause a serious problem. The wireless mesh network is the only technique for solving this problem.
The inventors have suggested an Intermittent Periodic Transmit method (hereinafter referred to as “IPT”) that realizes a highly efficient packet relay transmission in a multihop network including a plurality of nodes (see Patent Document 1, Patent Document 2, Patent Document 3).    [Patent Document 1] Japanese Patent Laid-Open No. 2005-143046    [Patent Document 2] Japanese Patent Laid-Open No. 2006-157501    [Patent Document 3] Japanese Patent Laid-Open No. 2006-319787